Why did Gulliver conclude that all the scientists in the academy at Lagado were insane? On the basis of his conclusion, draw a character sketch...

Gulliver concludes that the scientists working in Lagado are crazy because the types of experiments that they do are of no real use to anyone.  Trying to extract sunlight from cucumbers, returning human fecal matter to the original foods that comprise it, and figuring out a way for humans to carry everything to which they might possibly refer to with language so that they no longer have to speak a language are not good uses of the academy's time, money, resources, and brain power.  These experiments in no way benefit humanity, and so the people who insists on conducting them seem to be somewhat delusional to Gulliver.

In this sense, then, perhaps Gulliver is not so completely ridiculous as we might believe him to be based on his descriptions of other places and customs and peoples.  If even he can see these experiments as insane, this shows us that he does have some sense, because this is certainly the opinion Swift expects us to form of them.  Gulliver does, in fact, have some intelligence.